This invention relates to a film supplying device, or a device for supplying a web of elongated flexible bag-forming material (herein referred to as "film"), for a form-fill-seal packaging machine for making packages by making bags and concurrently filling them with articles and sealing them.
With a so-called pillow type packaging machine, as shown in FIG. 1, which is a kind of such a packaging machine, the film F is pulled out of a film roll R around which it is wound and is passed over a diagonally disposed turn bar 15 such that its direction of transportation T is changed by 90.degree.. The turn bar 15 is moved in the axial direction of film roll R (shown by arrow X) according to its width W such that the center line of the film F will always pass over the centers of the guide rollers 3, 4, 5, 6 and 7 which guide the film F to a bag forming device S.
At the bag forming device S, the film F is passed over a former roller 8 to a former 9 by means of which the film F is bent into a tubular shape and its mutually overlapping side edges are sealed together by a longitudinal sealer 10 of a packaging device H. After the articles to be packaged are dropped into this tubularly shaped film F, a transverse sealer 11 seals the bag-shaped film F transversely and cuts it over the sealed area to produce individually separate filled bags B.
The film roll R is usually supported rotatably around a support shaft J1. With the kind of prior art packaging machine which requires each film roll to be loaded at a different position, depending on its length (or the width W of the film F wound therearound), it is time-consuming to properly adjust the position of the film roll R on the support shaft because the film roll R is usually large and heavy and hence is difficult to handle manually. In view of this problem, Japanese Patent Publication Tokkai 7-205934 disclosed a new technology according to which a film roll is placed on a positioning apparatus with a pair of plates for sandwiching the film roll and sliding it for correct positioning. This technology was not practical, however, because the mechanism for moving the two plates was complicated, besides being bulky.
Another problem to be dealt with has been that film rolls with different lengths must be used because the width of the film must be changed, depending on the size of the bags to be formed. FIG. 9 shows, as an example, prior art roll supporting device 20A on which film rolls Ra, Rb and Rc with different film widths Wa (small), Wb (medium) and Wc (large) are selectively loaded to the support shaft. When the smallest film roll Ra is set as shown in FIG. 9, the turn bar 15 (of FIG. 1) is placed at a position indicated by symbol 15a such that the film pulled out of it will change its direction of motion by 90.degree. so as to move in the axial direction of the film roll R (the X-direction) towards the bag forming device S (as shown in FIG. 1). For this purpose, the center line Oa of the film as it is pulled out of the film roll R passes through the center position O1a of the turn bar position 15a. Similarly, symbols 15b and 15c indicate the positions of the turn bar 15 when the film rolls Rb and Rc are loaded on the support shaft and the center lines Ob and Oc of the films with widths Wb and Wc will pass through the centers O1b and O1c of the turn bar positions 15b and 15c. When a small film roll Ra is replaced by a medium-sized film roll Rb, the distance by which the turn bar 15 should be moved is indicated by L5 (or (Wb-Wa)/2) which is relatively small. When the small film roll Ra is replaced by a large film roll Rc, however, this distance will be L6 (or (Wc-Wa)/2) which is quite large. In other words, as the difference in width of film between the smallest and the largest to be accommodated is increased, the mechanism for moving the turn bar 15 in the X-direction becomes correspondingly large and the packaging machine as a whole becomes also large.
When a film with a different width is used, the size of the former to be set in the bag forming device S must usually be changed also. As a small former 9a is replaced by a medium-sized former 9b and then by a large former 9c, as shown in FIG. 10, the former roller 8 must also be moved correspondingly from a closer position 8a to an intermediate position 8b and then to a farther position 8c. When a small film roll Ra is replaced by a medium-sized film roll Rb and the smaller former 9a is correspondingly replaced by the medium-sized former 9b, the distance by which the former roller 8 should be moved is L7, which is relatively small. When the small film roll Ra is replaced by a large film roll Rc and the smaller former 9a is replaced by the larger former 9c, however, this distance is L8, which is significantly larger than L7.
In summary, in order to be able to make bags with a wide range of widths, the packaging machine must be able to accommodate film rolls of different lengths and to move the turn bar and the former roller accordingly by much larger distances. This means that the mechanisms for moving the turn bar and the former roller become larger and the packaging machine itself becomes large.